1. Field of the Invention
The subject of the present invention is a facility for hot forging workpieces starting from bars.
2. Discussion of the Background
A facility is known for hot forging workpieces starting from bars which comprises a means for heating the bars, for example using an induction furnace, a means for longitudinally moving the bars in the said facility, a shearing machine for cutting, hot, to a defined length, billets intended to be forged by closed-die forging, and including a stop for setting the billet length and a means for holding the cut billet in order to direct it towards a forging die, a means for detecting ends of the bars and a means for rejecting the billets which have a length shorter than the planned length.
This facility detects the ends of the bars by identifying a space existing between the heated bars at approximately two or three bar lengths upstream of the shearing machine.
The means for identifying the ends of the bars comprises an optical camera or a charge-coupled sensor or else photoelectric sensors which indicate the space between the said bars.
This facility therefore has the main drawback of detecting only the ends of the bars.
Now, the detected clearance, existing between the bars at a distance of two or three bar lengths before the shearing machine, is generally absorbed by slip on account of the fact that the movement of the bars is a constant-speed movement, whereas the last bar at shearing moves sequentially, by being brought up against a stop before the shearing.
The distance between and the slip of the bars, pressing up against the bar being cut, lead to a significant error in determining the length and necessitates, on average, for safety reasons, at least three billets being rejected per bar, and sometimes five or seven.
The rejection of these billets therefore generates a significant loss of material, at least three empty-die forging operations per bar and a reduction in the output in terms of the number of forged workpieces per hour.